In order to develop an excellent performance UHV arrester

the author have studied the existence of limits of the practical requirements of ZnO varistor voltage gradient

and combining with the practical application demand of the UHV arrester

discussed the ZnO varistor voltage gradient limits related issues in detail.Research shows that the voltage gradients of ZnO varistors in UHV arresters are limited not only by the outer facts such as insulation distance and rated current of UHV arresters

but also by the inner fact of energy absorption densities of ZnO varistors.Higher voltage gradients of the ZnO varistors lead to higher requirements for their energy absorption densities.The theoretical limitation of energy absorption density of a ZnO varistor is 517 J/cm3

and the related theoretical limitation of its voltage gradient is 686 V/mm.For the ZnO varistors in the UHV arresters with porcelain insulation

composite insulation or GIS insulation

their ideal voltage gradients should be 213

300 V/mm or 426 V/mm

while their energy absorption densities should be 150

226 J/cm3 or 301 J/cm3 at least

respectively.